.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
.\" * are also available at https://curl.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.\"
.TH CURLOPT_UNIX_SOCKET_PATH 3 "09 Oct 2014" "libcurl 7.40.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_UNIX_SOCKET_PATH \- set Unix domain socket
.SH SYNOPSIS
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UNIX_SOCKET_PATH, char *path);
.SH DESCRIPTION
Enables the use of Unix domain sockets as connection endpoint and sets the path
to \fIpath\fP. If \fIpath\fP is NULL, then Unix domain sockets are disabled. An
empty string will result in an error at some point, it will not disable use of
Unix domain sockets.

When enabled, curl will connect to the Unix domain socket instead of
establishing a TCP connection to a host. Since no TCP connection is created,
curl does not need to resolve the DNS hostname in the URL.

The maximum path length on Cygwin, Linux and Solaris is 107. On other platforms
it might be even less.

Proxy and TCP options such as
.BR CURLOPT_TCP_NODELAY "(3)
are not supported. Proxy options such as
.BR CURLOPT_PROXY "(3)
have no effect either as these are TCP-oriented, and asking a proxy server to
connect to a certain Unix domain socket is not possible.

The application does not have to keep the string around after setting this
option.
.SH DEFAULT
Default is NULL, meaning that no Unix domain sockets are used.
.SH PROTOCOLS
All protocols except for file:// and FTP are supported in theory. HTTP, IMAP,
POP3 and SMTP should in particular work (including their SSL/TLS variants).
.SH EXAMPLE
Given that you have an nginx server running, listening on /tmp/nginx.sock, you
can request an HTTP resource with:

.nf
    curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, "/tmp/nginx.sock");
    curl_easy_setopt(curl_handle, CURLOPT_URL, "http://localhost/");
.fi

If you are on Linux and somehow have a need for paths larger than 107 bytes, you
could use the proc filesystem to bypass the limitation:

.nf
    int dirfd = open(long_directory_path_to_socket, O_DIRECTORY | O_RDONLY);
    char path[108];
    snprintf(path, sizeof(path), "/proc/self/fd/%d/nginx.sock", dirfd);
    curl_easy_setopt(curl_handle, CURLOPT_UNIX_SOCKET_PATH, path);
    /* Be sure to keep dirfd valid until you discard the handle */
.fi
.SH AVAILABILITY
Since 7.40.0.
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_OPENSOCKETFUNCTION "(3), " unix "(7), "
